It is generally known that in the course of preparing cardio CT pictures with the aid of multirow detectors that are moved spirally around a patient a table feed is set such that each desired slice position can be reconstructed in a scanning area, selected by the user, relating to each heart phase. The temporal reference between the measured value projections and the heartbeat of the patient is generally determined in this case by an ECG or another rhythm signal of the beating heart. The reconstruction of a first or last image slice in this case requires a certain runup distance of the spiral or, correspondingly, a certain runout distance of the spiral. To date, this runup distance or runout distance of the scanning has been selected to be constant independently of the heart rate of the patient. An unnecessarily high dose burden can thereby come about for the patient.